Corrosion resistant pump



Oct. 12, 1965 v. MANDORF, JR., ETAL 3,211,108

' CORROSION RESISTANT PUMP Filed NOV. 1, 1963 INVENTORS VICTOR MANDORF JR CRESCENZO F' FULGENZI A T TORNE V United States Patent 3,211,108 CORROSIGN RESISTANT PUMP Victor Mandorf, Jr., and Crescenzo F. Fulgenzi, Fostoria,

Ohio, assignors to Union Carbide Corporation, a corporation of New York Filed Nov. 1, 1963, Ser. No. 320,692 6 Claims. (Cl. 103-216) This invention is concerned with a corrosion resistant pump, and more particularly it relates to a pump composed of a dense, hard refractory material which is suitable for use in pumping corrosive and erosive fluids such as liquid fuels, and molten metals such as high melting point die casting alloys, for instance, aluminum and the like.

Although most pumps are of a general construction and are suitable for a wide range of applications, there is a need in some industries for pumps of special construction and of particular materials. For instance, impervious graphite pumps have been specifically designed and developed .to pump certain fluids, such as acids, salt solutions, organic compounds, alkalies and various oxidizing chemicals. Many types of pumps have also been fabricated to pump other corrosive materials. However broad this class of materials which can be succcessfully pumped may seem, in the case of pumping corrosive and erosive high melting point alloys such as molten aluminum in particular, there has been extreme difficulty in achieving such pumping means inasmuch as most materials of construction including some refractories are attacked by the molten metal.

Presently, it is well known that the die casting industry has tried to develop numerous pumps for use in the hot chamber die casting of aluminum; but unfortunately it has yet to produce a satisfactory pump. This is so since the materials heretofore available particularly the refractories were not strong enough and were unable to stand up to the high pressures-high temperatures and particularly to the corrosive and erosive activtiy of molten aluminum.

In the, past, pumps made of various refractory materials have been tried but they have proved unsuccessful since molten aluminum attacks refractory materials to varying extents. In general, due to the rubbing action between the pumps piston and cylinder or housing and the action of the molten aluminum the pump assembly erodes and corrodes very rapidly. An example of one 'of the materials suggested for use in a shot cylinder of a hot chamber aluminum die casting machine is disclosed in US. Patent No. 3,067,146. This patent teaches aluminum resistant articles comprising from about to about 80% by weight of titanium diboride, the balance being aluminum oxide containing a 1 to 3% addition of chromic oxide. However, this material does not have the optimum characteristics desired of a refractory used for the elements of a pump continuously submerged in a molten metal bath, such as the basin or pot of the hot-chamber aluminum die casting machine disclosed in copending United States application, Serial No. 320,- 693, filed November 1, 1963, which application is assigned to the same assignee as the present invention.

It is, therefore, the principal object of the invention to provide a corrosion resistant pump suitable for .use in pumping corrosive and erosive fluids.

Another object of the invention is to provide a corrosion resistant pump that is capable of pumping high 3,211,108 Patented Oct. 12, 1965 melting point die casting alloys particularly when submerged in the molten metal.

Another object of the invention is to provide a corrosion resistant pump suitable for use in a die-casting machine.

In accordance with the invention, a corrosion resistant pump composed of relatively stable, hard, dense, inert refractory material consisting of substantially pure titanium diboride exhibits improved characteristics and exceptionally long life. It has been found that the useful life of pump members, particularly those members subjected .to turbulent and agitated streams of molten aluminum is much longer than any existing corrosive resistant pumps if the pump members are composed of substantially pure titanium diboride. By this it is meant that the total amount of impurities, i.e. nitrogen, oxygen and carbon remaining in the titanium diboride subsequent to a purification process of basically raw titanium diboride which is commercially available, is less than about 1%, the balance being titanium and boron.

Other features and advantages of the invention will be apparent from a reading of the accompanying specification and claims in conjunction with the associated drawing in which:

FIGURE 1 is an elevational view partially in section of a pump constructed in accordance with the invention.

FIGURE 2 is an elevational view partially in section of a modified pump assembly suitable for use in ladling molten aluminum from a bath and conveying same to a desired locality, including areas considerably above the level of the molten metal bath.

Commercially available titanium diboride has been found to comprise in weight percents: titanium (65.3 68.1), boron (27.8-30.8), carbon (32-25), nitrogen (.28-2.1) and oxygen (.442.8), such material may suitably be purified by adding boron nitride to the titanium diboride material, followed by heating to about 1900 C.- 1950 C. for a sufficient length of time such that the reaction is complete. At this temperature range the boron nitride reacts with the impurities to form volatile components which are lost as exhaust gases. Such volatile components are primarily C0, C0 and N The amount of boron nitride added to the titanium diboride material should be sufficient so as to reduce the nitrogen, carbon and oxygen content .to less than about 1%. This purification procedure is fully disclosed in copending application Serial No. 245,394, filed December 18, 1962 and assigned to the same assignee as the present invention.

The substantially pure titanium diboride used in the practice of the invention has a theoretical density of approximately 4.5 grams/cc. or 282 lbs./ft The elements of the pumps described hereinbefore as made of titanium diboride are the plungers and cylinders or body portions. These components are fabricated to or more of theoretical density so that a non-porous structure results thus precluding the aluminum metal from impregnating and leaking through the pores thereof. The scratch hardness of pure titanium diboride is measured by Mohs scale of minerals, i.e. its rating of 9+ indicates that it will scratch a sapphire but not a diamond. This material also has a micro hardness of about 3400 kg./sq. mm; its electrical conductivity is excellent. Due to the materials extreme hardness, it can only be machined by diamond grinding or by electrolytic grinding techniques.

3 Other physical properties of the pure titanium diboride are as follows:

Coefficient of thermal expansion between and 1500 C. is 9 10 C.

Melting point 2900 C. Tensile strength (to 2000 C.) 20,000 p.s.i. Elastic modulus 60 l0 p.s.i. Electrical resistivity, microhm centimeters l5. Compressive strength 250,000 p.s.i. Porosity, percent 3. Flexure strength 3035,000 p.s.i.

up to 2000 C.

Particle or grain size (Average) 10 micron, Thermal conductivity (cal./sec./cm. /cm./ C.) 0.069.

The following table illustrates the superior wear resistance of the substantially pure titanium diboride over other refractories such as TiB -CrB The various test samples or specimens save the SiC coated graphite were rubbed against a standard sample of silicon carbide coated graphite while immersed in molten aluminum at approximately 200 rpm. and at a 10 p.s.i. load; the SiC coated graphite specimen was rubbed against TiB -CrB The type of graphite used for these specimens was a fine grain structure graphitized coke base material. This setup simulated the conditions that a pump assembly similar to those disclosed herein would experience in a hot chamber die casting machine. The wear rates of each sample were measured and the average wear rate for the runs is indicated in the following table.

Alumi- Wear Referring now to the drawing, and more particularly to FIGURE 1, there is shown a preferred pump assembly, generally indicated by the numeral 10. It may be seen that the form of the pump assembly illustrated comprises a plunger or piston 12 and a cylindrical portion hereinafter referred to as the cylinder 14. The cylinder 14 is provided with a bored chamber 16, an inlet 18 and an outlet 20. At the outlet 20, a suitable valve-like device 21 can be disposed so as to control the flow therethrough. It should be realized that the inlet may be located above as well as below the outlet and that the cylinder 14 may be square or rectangular in shape, but the bored chamber 16 .is preferably cylindrical in shape. The piston 12 is shown secured to a piston rod 22 of a conventional power cylinder 23 or the like. It is not believed necessary to further describe the details of construction or the operation of the pump assembly 10, inasmuch as such devices are well-known to those skilled in the art, and since no further description of it is required for an understanding of the present invention.

Another modification of the invention is illustrated in FIGURE 2. As shown there, a metering or ladling pump 24 composed of substantially pure titanium diboride is suitable for use in metering and pumping a charged amount of molten metal into the pouring slot of a coldchamber die casting machine. The pump 24 comprises a cupped shaped cylindrical body 26 having a cylindrically bored chamber 28 and an .inlet port 30 for enabling said chamber to be filled. The piston 32 is made to slidably fit into the chamber 28 of the body 26. An outlet passageway 34 in the piston 32 enables the molten metal to escape under pressure from the chamber 28 as the piston 32 isbrought down during the pumping cycle. A valve like device 36 may suitably be disposed in the passageway 34 to permit sutlicient pressure to be built up and also to govern the How of metal to the exit portion 38 of the passageway 34. In using the pump 24 as a metering pump no valve is needed inasmuch as the pump may be calibrated to meter a desired change by micrometers adjustments of the stroke or by other suitable means. Any suitable trough 40 may be used to direct the molten material to the desired location as for instance the pouring slot of a cold-chamber die casting machine (not shown). Of course, the trough may be heated up if necessary to preclude the molten metal from partially freezing and becoming slushy. If desired, the piston 32 may be so designed that the outlet passageway 34 can be directed to the pouring slot of the machine without the necessity of a trough. No further description is thought to be necessary since this type of pump and its operation is basically analogous to the pump of FIGURE 1.

In the practice of the instant invention, the elements of the pump which are to be .in rubbing frictional contact with the molten metal, i.e. the pistons 12 and 32 of FIGS. 1 and 2 respectively, and the cylinder 14 of FIG. 1 and the body 26 of FIG. 2 are composed of substantially pure titanium diboride (TiB containing less than about 1% of adventitious constituents.

Articles consisting of substantially pure titanium diboride may be fabricated into many diflerent shapes by hot pressing or by isostatic molding and then subsequently sintering and by other techniques used in the ceramic industry. This material exhibits great strength at elevated temperatures, is more oxidation resistant and less brittle than many other ceramic refractory materials. Cylinders ranging from about one inch in diameter to about twenty inches .in diameter have been fabricated in accordance with the procedures described above and other conventionally known methods. Stock length as great as from about 12 to about 16 inches long have been made.

Although the invention has been specifically directed toward a reciprocating type of pump, other applications will become apparent to one skilled in the art such as rotary screw or auger type pumps, and centrifugal pumps having impeller blade means.

What we claim is:

1. A pump suitable for pumping molten high melting point alloys comprising a body containing an inlet aperture and an outlet aperture, said inlet and outlet apertures communicating by means of a passageway and means for forcing said molten alloy from said body via said passageway; said body and said means being composed of substantially pure titanium diboride containing less than one percent of adventitious constituents.

2. A pump suitable for pumping molten high melting point alloys comprising a body containing an inlet aperture and an outlet aperture, said inlet and outlet apertures communicating by means of a passageway and a piston for forcing said molten alloy from said body via said passageway; said body and said piston being composed of substantially pure titanium diboride and containing less than one percent of adventitious constituents.

3. A pump suitable for pumping molten aluminum comprising an annular shaped body having an inlet aperture and an outlet aperture at its lower end thereof, said outlet aperture and said inlet aperture communicating by means of a bored pump chamber and a piston slidably engaged with said bored chamber for urging said molten aluminum from said chamber to said outlet; said body and said piston being composed of substantially pure titanium diboride containing less than one per cent of adventitious constituents.

4. A pump suitable for pumping molten aluminum comprising in combination, a cupped shaped body, an inlet aperture in the side wall of said body, a piston axially reciprocable within and relative to the bore of said cupped shaped body and connected to means for actuating said piston, said piston having a passageway running from the bottom end thereof to an exit aperture in the side of said piston, said piston during longitudinal reciprocative movement in said bore urges said metal up into said passageway to said exit aperture; said body and said piston being composed of substantially pure titanium diboride containing less than one percent of adventitious constituents.

S. The combination with a power cylinder including cylinder means having a work member and ram means mounted for longitudinal reciprocative movement in said cylinder means; means forming with said cylinder and said ram a passageway for filling said chamber with a fluid to be pumped when said ram is operable upwardly and discharging same when said ram is operable downwardly; said cylinder and said ram means being composed of substantially pure titanium diboride containing less than one per-cent of adventitious constituents.

6. The combination with a power cylinder including cylinder means having a work chamber and ram means mounted for longitudinal reciprocative movement in said cylinder means; means forming with said cylinder and said ram a passageway for filling said chamber with a fluid to be pumped when said ram is operable upwardly References Cited by the Examiner UNITED STATES PATENTS Golyer 75-202 2,077,239 4/37 Hinnuber 75 202 2,120,562 1/38 Laise 75 202 2,874,065 2/59 Herz et al. 75-202 2,996,793 8/61 Jayne 75 202 OTHER REFERENCES Article of the Washington Evening Star of August 31, 1953, on the editorial page, by Thomas R. Henry.

20 KARL J. ALBRECHT, Primary Examiner.

JOSEPH H. BRANSON, JR., Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,211,108 October 12, 1965 Victor Mandorf, Jr. et ale It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line for "member" read chamber Signed and sealed this 51st day of May 1966 ST W. SWIDER 1g Officer EDWARD J. BRENNER Commissioner of Patents 

1. A PUMP SUITABLE FOR PUMPING MOLTEN HIGH MELTING POINT ALLOYS COMPRISING A BODY CONTAINING AN INLET APERTURE AND AN OUTLET APERTURE, SAID INLET AND OUTLET APERTURES COMMUNICATING BY MEANS OF A PASSAGEWAY AND MEANS FOR FORCING SAID MOLTEN ALLOY FROM SAID BODY VIA 